University of Colorado Colorado Springs

About: University of Colorado Colorado Springs is a education organization based out in Colorado Springs, Colorado, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 6664 authors who have published 10872 publications receiving 323416 citations. The organization is also known as: UCCS & University of Colorado at Colorado Springs.

Delta-sigma oversampled ultrasound beamformer with dynamic delays

Abstract: The principles of oversampling are exploited in a simple beamforming architecture using a single bit delta-sigma (/spl Delta/C) analog to digital converter (A/D) on every channel. The high sampling rate required for the single bit A/D provides adequate delay accuracy for high quality beamforming using elementary sample manipulations. Images produced with this beamformer exhibit significant artifacts directly related to dynamic focusing. However, a simple digital recording technique following delays permits dynamically focused beamforming without degrading image quality. The simplicity of this beamformer compared to conventional methods may facilitate very large channel count or low power beamformers suitable for 1.5-D arrays or portable scanners.

Bypass-zone tempestite facies model and proximality trends for an ancient muddy shoreline and shelf

Abstract: Member 2 of the late Precambrian to Lower Cambrian Chapel Island Formation of southeast Newfoundland was primarily deposited in storm-influenced, nearshore and shelf environments along a fine-grained coastline. Deposition took place within or adjacent to a deltaic system that supplied abundant silts and clays. Thin-bedded graded sandstone beds, hummocky cross-stratified beds, and a variety of very thin conglomerate units contain evidence for deposition by storm currents. Sedimentological and stratigraphic evidence is used to reconstruct the relative paleobathymetric position of the three major facies in member 2. The Gutter Cast Facies is a shallow-subtidal deposit characterized by very thin sandstone laminae and abundant pot and gutter casts. The Siltstone-Dominated Facies contains more laterally extensive thin-bedded sandstones and fewer erosional features, and was deposited in the inner shelf. The Sandstone-Dominated Facies consists of thin to medium, graded and hummocky cross-stratified sandstone beds deposited in a more distal shelf setting, but above storm wave base. The facies model and set of proximality trends developed for member 2 deposits may be applicable to other storm-influenced fine-grained shorelines. In this model, the shallow subtidal is a zone of throughput with high-velocity, sediment-laden flows eroding deep narrow scours (gutter casts) and depositing very little sand outside of these scours. As the storm-generated flows move into deeper water they decelerate, resulting in less erosion of the sea floor and depositing thicker and more continuous sand beds (Siltstone-Dominated Facies). Further from shore, bed thickness reaches a maximum (Sandstone-Dominated Facies) and hummocky crossstratification is abundant. Even more distally, bed thickness decreases again (represented by thinly laminated siltstones of the overlying member 3). Analysis of sedimentary structures and paleocurrent data suggests deposition by storm currents that transported sediment nearly perpendicular to shore.

Classification of the line-soliton solutions of KPII

Abstract: In the previous papers (notably, Kodama Y 2004 J. Phys. A: Math. Gen. 37 11169–90, Biondini G and Chakravarty S 2006 J. Math. Phys. 47 033514), a large variety of line-soliton solutions of the Kadomtsev–Petviashvili II (KPII) equation was found. The line-soliton solutions are solitary waves which decay exponentially in the (x, y)-plane except along certain rays. In this paper, it is shown that those solutions are classified by asymptotic information of the solution as |y| → ∞. The present work then unravels some interesting relations between the line-soliton classification scheme and classical results in the theory of permutations.

Random walk on the infinite cluster of the percolation model

Abstract: We consider random walk on the infinite cluster of bond percolation on ℤ d . We show that, in the supercritical regime whend≧3, this random walk is a.s. transient. This conclusion is achieved by considering the infinite percolation cluster as a random electrical network in which each open edge has unit resistance. It is proved that the effective resistance of this network between a nominated point and the points at infinity is almost surely finite.

Timing adjustment control for efficient time division duplex, frequency division duplex or hybrid time division duplex/frequency division duplex communication

Abstract: A system and method for time division duplex communication over a single frequency band wherein guard time overhead is reduced by active adjustment of reverse link transmission timing as a function of round trip propagation time. A time frame is divided into a plurality of time slots, during each of which the base station transmits to a user station and the user station transmits to the base station. Communication is initiated by a round trip timing transaction. In response to a general polling message from the base station, a user station seeking to establish communication transmits a short reply message. The base station calculates the distance of the user station by measuring the propagation delay with respect to receipt of the reply message. The base station sends a timing adjustment command to the user station instructing the user station to advance or retard its timing according to the calculated distance, so as to minimize guard times between time slots. Thereafter, the base station monitors the user station transmissions and periodically commands the user station to advance or retard its timing in a like manner. The user station may transmit a control preamble at the start of each time slot to allow the base station to perform round trip timing calculations, and/or to allow adjustment of user station power or antenna selection. The system is capable of independently selecting frequency bands and time slots for a duplex communication link, providing a pure Time Division Duplex (TDD) mode, Frequency Division Duplex (FDD mode or Hybrid Time Division Duplex/Frequency Division Duplex (TDD/FDD) mode.